Pull-type tobacco harvesters have been used by tobacco farmers for some time to harvest tobacco. Generally, a pull-type tobacco harvester includes a mainframe having a tongue that projects therefrom and connects to a tractor. In addition, there is provided a leaf defoliating unit on the mainframe and a conveyor assembly for conveying tobacco leaves harvested by the defoliator assembly, the conveyor assembly functioning to convey the leaves generally upwardly and rearwardly to where they are discharged into a trailer or other receptacle disposed behind the pull-type harvester.
Because of the nature of tobacco and the row planting scheme employed by tobacco farmers, pull-type tobacco harvesters are designed to be pulled at an offset position relative to the tractor pulling the harvester through the field. The fact that the tobacco harvester is offset with respect to the tractor gives rise to a number of problems and concerns. Because tobacco is a row crop, it is appreciated that the harvester must be aligned with the row or rows being harvested such that that the row of tobacco stalks is precisely aligned with the defoliator unit. This is important because as the tobacco stalks pass through the defoliator unit, it is important that only the leaves be defoliated from the stalks and that the stalks remain generally intact. However, because of the offset relationship of the harvester with respect to the tractor, precise row alignment is difficult to achieve and maintain even under the best of conditions.
There are a number of factors that contribute to the difficulty of maintaining row alignment with the defoliator unit. First, the operator is not located closely adjacent the defoliator unit and the row of tobacco being harvested. Indeed, the operator is stationed on a tractor that is a considerable distance forward of the defoliator unit and offset to one side. Therefore, it is difficult for the operator to continuously precisely judge the alignment between the throat or entry way of the defoliator and the row of tobacco being harvested. Next, it is a common occurrence that tobacco stalks are not always maintained in a straight upright position in the row. Often, the stalks can be blown to one side or simply can grow in a direction that causes some portion of the stalks to project outside of the true plane of the tobacco row. Finally, one of the most important factors contributing to defoliator-row alignment problems, is the common tracking problems that one finds with an offset pull-type tobacco harvester. Because of the offset relationship of the harvester and the orientation of the tractor with respect to the harvester, it is not unusual for the harvester to fail to track accurately through the tobacco field. This tracking problem is even more of a concern in wet, hilly, or sandy soil conditions. In such conditions, the harvester tends to slip and slide from one side to the other and because there is not a great deal of room for misalignment between the row being harvested and the throat of the defoliator, it follows that even a few inches of misalignment can result in the defoliator unit cutting and destroying entire row segments, all of which results in damage and crop loss to the tobacco farner.
Therefore, there has been and continues to be a need for a pull-type tobacco harvester that exhibits superior tracking ability even in wet and hilly conditions.
As discussed above, tobacco harvesters of all types use what is commonly referred to as a knife-type defoliator. W. E. Splinter in U.S. Pat. No. 3,093,949 discloses a tobacco leaf defoliator assembly of the knife type. Structurally, the Splinter knife head defoliator comprises a pair of inclined and laterally spaced defoliator side units that in operation are generally disposed on opposite sides of a tobacco row and are designed to allow individual stalks of the row to pass therethrough as the defoliator assembly is moved along the tobacco row by a tobacco harvester.
From a study of the Splinter patent, it can be seen that as the defoliator assembly moves along the tobacco row, certain sets of knife blades move inwardly from opposite sides of the row to project through the plane of the tobacco row and adjacent and between the respective stalks passing through the defoliator assembly. As the knife blades move to a position where they project adjacent and between successive stalks, the defoliator assembly then drives these blades upwardly and forwardly relative to the harvester. As the blades move upwardly adjacent respective stalks, they engage certain tobacco leaves extending from the stalks and defoliate the leaves from the stalks, while the forward component enables the blade to move forwardly as the harvester moves forwardly.
The Splinter type tobacco leaf defoliator works extremely well in tobacco crops where the stalks are all upright and aligned so as to extend in the same plane. But in the practical world, one seldom finds tobacco fields where all of the stalks of a tobacco row project upright and fall precisely within the plane of the row. In the real world, one finds stalks of tobacco that have been blown over and are tilted out of the plane of the row. This can make harvesting tobacco with the Splinter knife-type defoliator difficult. As pointed out above, there is not a great deal of tolerance for row misalignment with respect to the defoliator assembly. When the defoliator unit reaches field areas where the stalks are blown or otherwise tilted to one side, it is common to find that the defoliator unit simply tends to cut and chop the stalks and consequently instead of harvesting the leaves, this situation results in substantial crop loss. In many cases, the tobacco stalks are simply cut and chewed apart and left laying in the field. In some cases, the knife-type defoliator actually cuts stalk portions of the tobacco and the stalk portions fall onto the conveyor assembly where they are conveyed into the tobacco leaf receptacle. Both cases are quite undesirable for obvious reasons.
Therefore, there is and continues to be a need for a knife-type defoliator that will tend to upright the stalks and align them in such a fashion that the leaves can be harvested without the stalks being cut and the tobacco crop being destroyed.